For the forthcoming year, we would like to further delineate the relationship between plasma bradykinin and the renin-angiotensin system. In normal individuals, there is a close parallel between plasma bradykinin and renin activity in response to physiologic manipulations. In patients with essential hypertension however, this relationship is more variable. In the first fifteen patients studied, nine patients showed a decrease in plasma bradykinin, two patients showed no change and in the remaining four patients it actually increased in response to sodium loading. As expected the PRA in all fifteen patients were suppressed with sodium loading. This suggests that patients with essential hypertension represents a nonhomogeneous group. Currently we are studying a greater number of patients to better categorize them into subgroups. Furthermore, we are trying to study the response of each subgroup to different antihypertensive medications such as diuretics, propranolol, etc.